Question

What are isotops ? How does the existence of isotopes contradict Dalyon's atomic theory

Answer 1

each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, and hence differ in relative atomic mass but not in chemical properties; in particular, a radioactive form of an element.

Answer 2

1)atoms having same atomic no. but different atomic mass;2)no